[Extract] Twenty years ago British GP Iona Heath observed that one of the key roles of the GP was to help protect people from the unnecessary diagnosis of disease. Perhaps the biggest challenge for doctors who take that role seriously comes from expanding disease definitions. The current definition of ‘chronic kidney disease’ labels 10% of the adult population as having the condition. New criteria almost triple the number of pregnant women labelled as having gestational diabetes. Thresholds defining attention deficit hyperactivity disorder continue to fall, meaning more children and adults will be diagnosed.